1. Field of the Invention
The subject invention is directed generally to retractable aircraft landing gear, and more particularly, to a locking mechanism for preventing a compressed shrink shock strut from transitioning into an extended position within the wheel well of an aircraft.
2. Background of the Related Art
Retractable landing gear for aircraft are well known in the art. In general, retractable landing gears include an elongated shock strut having an upper end that is pivotally mounted to the frame of the aircraft about a retraction axis for pivotal displacement between a vertical, downwardly extending, landing and ground support position, and a horizontal, retracted position nested within a wheel well in a lower surface of the aircraft wing or fuselage.
In such landing gears, the shock strut includes telescopically disposed cylinder and piston members defining a pneumatic or hydraulic spring chamber. Pressure within the chamber biases the strut toward a telescopically extended condition. When landing or at rest on the ground, the weight of the aircraft on the landing gear compresses the shock, forcing the strut to a relatively shortened condition, which may be a number of inches shorter than the extended condition. With the aircraft airborne and the landing gears down, the unloaded gears and associated shock struts assume their fully extended position. For sustained flight, the fully extended landing gears are rotated into the retracted position to reside within the wheel wells of the aircraft.
Although aircraft have been designed to accommodate retracted landing gear with fully extended struts, such a configuration does not always permit the most advantageous placement of the landing gear and its supporting structures within a wheel well. Moreover, the space within the wheel well of an aircraft is often limited due to design constraints. It is generally desirable therefore to minimize the amount of space required by the retractable landing gear.
One approach to saving space in the wheel well is to shorten the length of the landing gear before or during its retraction cycle into a stowed position. Examples of prior art shock struts capable of being compressed into a shortened state for efficient stowage in a wheel well of an aircraft are disclosed in U.S. Pat. No. 4,047,681 to Hartel and U.S. Pat. No. 5,908,174 to Churchill et al.
When the length of a landing gear is shortened or otherwise shrunk for retraction, it is possible that the mechanism that compressed the shrink shock strut could fail, allowing the strut to decompress and extend back to its fully extended condition. If this occurs while the landing gear is retracted within the wheel well, then it is likely the strut will become jammed in the wheel well, rendering it unable to deploy for landing the aircraft. This would lead to a gear up landing, which is highly undesirable as it could cause further damage to the landing gear as well as the aircraft itself.
Efforts have been made to prevent a shortened or shrunken landing gear shock strut from decompressing into a fully extended position within the wheel well of an aircraft in the event of a system failure. For example, it is known to provide a catch mechanism within the wheel well to prevent the upper torque arm of the landing gear from rotating past a certain point in its travel, and thereby hold the strut from reaching a fully extended position within the wheel well in the event of a compression system failure. With this prior art method, the upper torque arm of the landing gear is loaded in such a manner that the strut is still permitted to extend well beyond its shrunk condition. In addition, this prior art method requires excessive room and additional structure within the wheel well.
It would be beneficial therefore to provide a mechanism to prevent movement of a shortened or shrunken shock strut into a fully extended condition while it is retracted within the wheel well of an aircraft, that creates a relatively stiff load path when preventing the strut from extending, and which takes up a minimal amount of space with the wheel well. The shrink shock strut locking mechanism described and illustrated herein provides these and other benefits.